Accurate placement of pedicle screws is a key component of spine surgery. The goal of this study is to evaluate the accuracy and precision of a 3-dimensional (3D) printed patient-specific instrumentation (PSI) guide in improving pedicle screw trajectory placement for a first-time user.

A computed tomography scan of a cadaveric spine was obtained and 3D reconstructed virtually. One pedicle at each vertebra was randomized to the PSI or freehand (FH) grouping. Screw trajectories were virtually planned for T1-L5 vertebral levels. A junior orthopaedic surgery resident used the PSI to place a screw at 17 vertebral levels and then returned on a separate day to place screws using FH technique. No adjustments from the initial placement were allowed. Postoperatively the spine was rescanned and analyzed by a blinded senior attending surgeon for perforation, adequacy of placement, and likelihood of unfavorable outcome. The PSI grouping was analyzed objectively for deviation from the preoperative plan.

Five of the FH screws were deemed to likely result in paralysis or major neurovascular injury vs zero in the PSI grouping (p-value 0.045). The mean PSI placement time was 47.9 s faster per level than the FH placement time (145.2 ± 74.4 vs 193.1 ± 43.0 s; p-value 0.032). The PSI trajectories were accurate within 2.75 mm and 9.0 degrees of the planned trajectories (p-value 0.045; p-value 0.036).

The PSI system appears to offer a relatively inexpensive, user-friendly, and sufficiently accurate solution to pedicle screw placement for even a novice surgeon using the technology for the first time.